drm/udl: Implementation of atomic cursor drm_plane

[Daniel Vetter]

On Mon, Jun 24, 2024 at 09:28:29AM +0200, Thomas Zimmermann wrote:
> Hi
> 
> Am 24.06.24 um 09:10 schrieb lukasz.spintzyk at synaptics.com:
> > This brings cursor on DisplayLink USB2.0 device on ChromeOS compositor that requires either crtc'c cursor_set callback
> > or cursor drm_plane. Patch was tested on ChromeOS and Ubuntu 22.04 with Gnome/Wayland
> 
> NAK on this patchset. UDL has no HW cursor support, so we won't implement
> this in the driver. Software blending should be done in userspace, where you
> have CPU SIMD available.

I think for drivers which do cpu upload and are vblank driven there's
maybe a case for kernel implemented cursors due to latency reduction if
the blending happens as late as possible. But udl just goes right ahead
and uploads, so this doesn't help I think. damage tracking should, but we
already have that.

So concurring here.
-Sima
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch